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Phytonutrients

Phytonutrients, phytochemicals or flavonoids (oftentimes used interchangeably) are chemical compounds that have been identified in foods as having potentially positive health benefits.

“Phyto”, originated from a Greek word meaning plant, highlights the active elements found in the skins of plant rich foods that are associated with the color, flavor, and smell of fruits and vegetables. They can also be found in some grains, legumes, nuts and teas.   While phytonutrients have not been classified as essential nutrients, such as vitamins and minerals, research suggests their benefits are medicinal.

What are they and where are they found?

There are many types of phytonutrients, some are more commonly known, for example Beta Carotene, while other compounds may be more unfamiliar, such as Anthocyanins.   One of the best ways to insure your diet is rich in phytonutrients is to build your meals around a variety of colors, no not M&M’s ™, but through a variety of fruits and vegetables. Phytonutrients are oftentimes classified or grouped by colors of the rainbow. The table listed below is a basic example of the rainbow classification of phytonutrients.

Phytochemical Source
Lycopene Tomatoes
Beta Carotene Carrots, Pumpkins
Vitamin C/Flavonoids Oranges/Lemons
Lutein Kale/Spinach/Mustard Greens
Folic Acid/Glucosinolates Broccoli/Brussel Sprouts/Cabbage
Anthocyanins/Flavonoids Grapes/Red Wine Blueberries/Strawberries
Allyl Sulfides Garlic/Onion/Chives

 

Benefits

Diets rich in fruits and vegetables, and therefore rich in phytonutrients, have been linked with prevention of chronic disease and more specifically, lower rates of cancer and coronary heart disease which are the top two causes of death in the United States (i, ii, iii). Phytonutrients are reported to have antioxidant and anticarciongenic properties and a wide spectrum of tumor blocking activities. (iii) There is also some evidence that specific phytonutrients may help prevent the formation or suppress specific potential carcinogens, which are substances that cause cancer. (i, iii) An example would be lycopene and prostate cancer.   Phytonutrients and their metabolites elicit a variety of positive biological activities, including hormonal action, stimulation of enzymes, anti-bacterial, and antioxidant properties (iv, v).

One of the most widely studied areas is the antioxidant benefits of phytonutrients. Antioxidants are defined as a substance that inhibits oxidation or the damage of cells by free radicals. Free radicals can lead to premature aging and chronic disease.   Phytonutrients help to prevent oxidative stress. Without enough phytonutrients to counteract oxidative stress, damaging free radicals lead to inflammation and toxicity in the body. (v) Inflammation is tied to chronic disease as well as weight gain, thus phytonutrients may also have a role in the fight against obesity.

 

The SAD Truth

It is estimated that greater than 5000 individual phytonutrients have been identified in fruits, vegetables and grains, but it is estimated that a much larger percentage still remain unknown and unidentified in whole foods. (iv) Phytonutrients are most commonly found in freshly harvested plant foods and they can be destroyed or removed by modern processing techniques, and some possibly some even by cooking. The Standard American Diet (SAD), comprised of mostly processed and packaged foods, is highly deficient in phytonutrients. We know that processing of foods destroys many natural health benefits of foods and phytonutrients are not excluded.   The absence or deficiency of phytonutrients in processed foods may contribute to increased risk of preventable diseases. (v)

 

Recommendations

Currently, optimal levels to include Recommended Daily Intakes/Allowances (RDI/RDA) have not been established for phytonutrients.   Despite not having dosing recommendations, adequate intake of whole fruits and vegetables can insure optimal levels of phytonutrients in the diet. Recommendations of 9-11 servings of whole fruits and vegetables per day should be encouraged, but most Americans struggle to achieve half of this recommendation in their daily diet.   Remember the processing of fruits or vegetables likely destroys phytonutrients; therefore aim for whole fruits and vegetables.

Bottom line: The medicinal benefits of phytonutrient are yet another reason to avoid the Standard American Diet and include high amounts of whole fruits and vegetables in the diet.

 

  1. 1. Liu, R. H. (2004) Potential Synergy of Phytochemicals in Cancer Prevention: Mechanism of Action.   Am Society for Nutritional Sciences J. Nutr. 134: 3479S-3485S.
  2. 2. Liu, R. H. (2003) Health benefits of fruits and vegetable s are from additive and synergistic combination of phytochemicals. Am. J. Clin. Nutr. 78:517S-520S.
  • 3. Kushi LH, Byers T, Doyle C, et al: American Cancer Society 2006 Nutrition and Physical Activity Guidelines Advisory Committee. American Cancer Society guidelines on Nutrition and Physical Activity for cancer prevention: risk of cancer with health food choices and physical activity. CA Cancer J Clin. 2006; 56 254-281.
  1. 4. Lampe, J. (1999) Health Effects of Vegetables and Fruits: assessing mechanism of action in human studies. Am. J. Clin. Nutr. 70; 3: 475S-490S.
  2. 5. Knekt, P. et al. (2002) Flavonoid intake and risk of chronic disease. Am J Clin Nutr.   76: 560-568.

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